The present U.S. patent application having at least one common inventor as
U.S. patent application Ser. No. 09/961,155 entitled xe2x80x9cSystem and Method for Auxiliary Contact Assemblyxe2x80x9d, and
U.S. patent application Ser. No. 09/961,159 entitled xe2x80x9cSystem and Method for Auxiliary Contact Assembly and Snap Mountingxe2x80x9d, and
U.S. patent application Ser. No. 09/961,156 entitled xe2x80x9cSystem and Method for Mounting a Moveable Contact in a Contact Block, and
U.S. patent application Ser. No. 09/961,158 entitled xe2x80x9cContact Block Assembly and Method of Assembling a Contact Block Assemblyxe2x80x9d, and
U.S. patent application Ser. No. 09/961,161 entitled xe2x80x9cPusher Assembly and Method of Assembling a Pusher Assembly,
U.S. patent application Ser. No. 09/961,160 entitled xe2x80x9cMovable Contact and a Method of Assembling a Pusher Assembly having a Movable Contactxe2x80x9d are filed with the U.S. patent and Trademark Office concurrently on Sep. 21, 2001, the entirety of each being incorporated herein by reference.
This invention relates to a contact assembly for use in an electrical switching apparatus designed to reduce the number of different parts required.
A conventional electrical switching apparatus in one known form typically comprises an electromagnetically actuable device having a magnetic core proximate an armature. Typically, a coil is electrically energized to draw the armature to the magnetic core. The electromagnetically actuated device may be a control relay, a contactor, a motor starter or the like. The armature is operatively associated with a movable device such as an actuator. With an electrical switching apparatus the actuator operates a contact assembly.
A contact assembly may be an integral component of the electrical switching apparatus or it may an auxiliary device to be added thereto. In either case, a housing typically supports an electrical contact and a pusher. The pusher is selectively actuated to operate the electrical contact. A typical electrical contact includes one or two stationary contacts mounted in the housing and a moveable contact mounted on the pusher.
In applications involving the making of an electrical contact by moving a moveable contact against a pair of stationary contacts, the moveable contact is typically mounted on the pusher and forced against a stop on the pusher by a contact spring.
In a normally closed contact, the pusher is typically held by the return spring with the movable contact touching the stationary contacts. To avoid arcing when the contact closes, the moveable contact is typically held against the stationary contacts by a contact spring which, in turn, is compressed by the pusher. When the pusher is forced by an external actuator away from the stationary contacts, then the return spring is compressed and the contact spring extends until the moveable contact hits its stop on the pusher and lifts off of the stationary contacts.
In a normally open contact, the pusher is typically held with the moveable contact off of the stationary contacts by a return spring. When the pusher is forced by an external actuator towards the stationary contacts, then the moveable contact touches the stationary contacts and is held against the stationary contacts by the force of a contact spring. Alternatively, the contact spring can be mounted to a housing and a return spring holds the pusher against the moveable contact in such a way that it holds the moveable contact off of the stationary contacts until the pusher is forced by an external actuator away from the stationary contacts, thus allowing the moveable contact to come to rest against the stationary contacts under the force of the contact spring.
In both the typical normally closed configuration and alternative normally open configuration, discussed above, the force or torque applied by the return spring on the pusher must be greater than the force or torque applied by contact spring on the pusher. Otherwise, in the typical normally closed configuration, the contact spring would not compress and there might be problems with arcing. In the alternative normally open configuration the contact spring would force the contact closed, even if no external force is applied. Thus, contact assemblies designed for these typical configurations use different spring designs for the contact spring and the return spring, requiring inventory of different parts and loss of economies of scale.
Accordingly, there is a need for a contact assembly for use in an electrical switching apparatus designed to reduce the number of different parts required.
In accordance with the invention there is provided a contact assembly for use in an electrical switching apparatus designed to reduce the number of different parts required.
Broadly, there is disclosed a contact assembly for use in an electrical apparatus comprising a housing and a pusher movably mounted in the housing. A movable contact is supported on the pusher. A stationary contact is provided in the housing proximate the moveable contact. A pair of identical springs are mounted in the housing. Means are provided for mounting one of the springs as a return spring biasing the pusher to a normal position and the other of the springs as a contact spring operatively associated with the moveable contact to force the movable contact against a stop associated with the pusher, so that force or torque produced by the return spring is greater than force or torque produced by the contact spring.
In accordance with one aspect of the invention the contact assembly provides a normally open contact configuration. The contact spring extends between a stop on the housing and the moveable contact.
In accordance with another aspect of the invention the contact assembly provides a normally closed contact configuration. The movable contact is mounted on a post extending from the pusher and the contact spring extends between the pusher and the moveable contact.
In accordance with a further aspect of the invention the pusher is movably mounted in the housing for linear movement and spacing between the housing and the pusher at the return spring is less than spacing between the housing and the moveable contact at the contact spring.
In accordance with still another aspect of the invention the pusher is movably mounted in the housing for rotary movement and spacing between a pivot point and the pusher at the return spring is greater than spacing between the pivot point and the pusher at the contact spring.
In accordance with yet another aspect of the invention a contact assembly for use in an electrical apparatus comprises a housing and a pusher movably mounted in the housing. A movable contact is supported on the pusher. A stationary contact in the housing is proximate the moveable contact. A return spring biases the pusher to a normal position. A contact spring operatively associated with the moveable contact forces the movable contact against a stop associated with the pusher. The contact spring and the return spring are of identical construction and are positioned in the housing so that force or torque produced by the return spring is greater than force or torque produced by the contact spring.
Further features and advantages of the invention will be readily apparent from the specification and from the drawings.